package com.wy.test.protocol.cas.endpoint.ticket.generator;

import java.security.SecureRandom;

/**
 * Implementation of the RandomStringGenerator that allows you to define the
 * length of the random part.
 *
 */
public class DefaultRandomStringGenerator implements RandomStringGenerator {

	/** The default maximum length. */
	public static final int DEFAULT_MAX_RANDOM_LENGTH = 35;

	/** The array of printable characters to be used in our random string. */
	private static final char[] PRINTABLE_CHARACTERS =
			"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345679".toCharArray();

	/** An instance of secure random to ensure randomness is secure. */
	private SecureRandom randomizer = new SecureRandom();

	/** The maximum length the random string can be. */
	private int maximumRandomLength;

	/**
	 * Instantiates a new default random string generator with length set to
	 * {@link #DEFAULT_MAX_RANDOM_LENGTH}.
	 */
	public DefaultRandomStringGenerator() {
		this.maximumRandomLength = DEFAULT_MAX_RANDOM_LENGTH;
	}

	/**
	 * Instantiates a new default random string generator.
	 *
	 * @param maxRandomLength the max random length
	 */
	public DefaultRandomStringGenerator(final int maxRandomLength) {
		this.maximumRandomLength = maxRandomLength;
	}

	@Override
	public int getMinLength() {
		return this.maximumRandomLength;
	}

	@Override
	public int getMaxLength() {
		return this.maximumRandomLength;
	}

	@Override
	public String getNewString() {
		final byte[] random = getNewStringAsBytes();

		return convertBytesToString(random);
	}

	@Override
	public byte[] getNewStringAsBytes() {
		final byte[] random = new byte[this.maximumRandomLength];
		this.randomizer.nextBytes(random);
		return random;
	}

	/**
	 * Convert bytes to string, taking into account {@link #PRINTABLE_CHARACTERS}.
	 *
	 * @param random the random
	 * @return the string
	 */
	private String convertBytesToString(final byte[] random) {
		final char[] output = new char[random.length];
		for (int i = 0; i < random.length; i++) {
			final int index = Math.abs(random[i] % PRINTABLE_CHARACTERS.length);
			output[i] = PRINTABLE_CHARACTERS[index];
		}

		return new String(output);
	}
}
